Watch List notes:

SAUDI ARABIA: 'Abd al-'Aziz b. Sa'ud, 1926-1953, AR riyal, [Makka al-Mukarraman], KM-18, standard obverse; the reverse has been reengraved by an artist or engraver, portraying an oil refinery, SARP above ("Saudi Arabian Refinery Plant"), dated 1364 / 1945 below, pierced at the top for suspension, AU. American oil workers stationed in Saudi Arabia from the 1940s to at least the 1970s often had a local engraver redesign one side of a silver coin, most commonly the riyal.

Estimate: 110-150 USD